Respiration in the burrowing brittlestar, Hemipholis elongata say (Echinodermata, Ophiuroidea): a study of the effects of environmental variables on oxygen uptake

The burrowing brittlestar Hemipholis elongata (Say) maintains a constant M(O2)of 3.79+/-1.47 micromol O(2) g(-1) h(-1) (for 0.2-0.3 g animals, mean+/-S.D., n=7), measured in the burrow, over a broad range of PO(2). Below the critical PO(2) of 37 mm Hg, M(O(2)) becomes dependent on the oxygen tension. M(O2) is a function of the size of H. elongata; the scaling exponent is 0. 83 and is similar to those reported for other echinoderms. The M(O2) of H. elongata is unaffected by removal from the burrow, by hypercapnia, by exposure to hydrogen sulfide, or by temperature change in the range from 20 to 32 degrees C. The relative insensitivity of H. elongata to these factors may be an adaptation to life in the highly variable estuarine and tidal creek environments where the animals are frequently found.     

Mechanics of branchial ventilation in the valviferan isopod Idotea wosnesenskii (Crustacea)

Idotea wosnesenskii Brandt, a valviferan isopod, has five pairs of pleopods within a branchial chamber enclosed by modified uropods (operculae). The pumping mechanism of resting isopods was videotaped to observe ventilation, and particularly to determine whether or not the swimming pleopods (first three pairs) and the gas exchange pleopods (last two pairs) have ventilatory roles. Observations on intact animals (to observe water flow into and out of the branchial chamber) and on animals with operculae propped open or with parts of their abdominal wall removed (to study the actual pumping movements of the pleopods) revealed that all five pairs of pleopods function in ventilation. The ventilatory stroke has two phases: an opening phase in which the pleopods move medially and ventrally, opening spaces between pleopods (analogous to the swimming recovery stroke), and a closing phase, wherein the pleopods move laterally and dorsally, reducing the gaps between succeeding pleopods (analogous to the swimming power stroke). Ventilatory strokes may be continuous or they may be separated by resting phases. Both the frequency and amplitude are variable: the frequency changes greatly due to the wide variation in resting phase duration. By opening the operculae the amplitude can increase so that ventilatory strokes grade into swimming strokes. The ventilatory stroke pattern at rest is generally similar to the swimming stroke pattern but differs in its slower and nearly simultaneous dorsoventral movements and its lower frequencies. Dye and particle movements around intact animals and those with exposed pleopods show that water typically takes about three strokes to pass through the branchial chamber.     

The behaviour of Corophium volutator (Crustacea: Amphipoda)

The behaviour of Corophium volutator (Pallas) is outlined. Swimming, crawling, burrowing and feeding activities are described in detail. Animals usually swim on their backs. Every few seconds, swimming alternates with passive sinking. Animals can crawl over surfaces in and out of water. Out of water they do so by a looping motion using their second antennae and telson. When out of water animals crawl away from light and down slopes. In water they swim towards light. Burrowing is initiated by rapid beating of the pleopods; the animal then sinks below the surface by a concerted action of pereiopods, pleopods, telson, uropods and second antennae; within a few minutes, a shallow burrow is formed. The formation of permanent burrows is dependant on particle size, on adhesive properties of detritus and primary films on sand particles, and on a secretion produced by the animal itself. Individuals can turn about in permanent burrows. The species is essentially a detritus feeder. Animals normally feed only when in their burrows, by using their second antennae to scrape material from the substrate surface into the entrance of the burrow. This material is then transported to the mouth by the feeding appendages and respiratory current. The behaviour of small and large animals differs; small animals burrow rapidly and permanently, and do not emerge spontaneously; furthermore, they only swim occasionally. Large animals swim more frequently, spend more time on the substrate surface, and periodically move burrows. It is suggested that new habitats are colonized by large animals which have already bred once.     

Denitrification and nitrogen fixation dynamics in the area surrounding an individual ghost shrimp (Neotrypaea californiensis) burrow system

Bioturbated sediments are thought of as areas of increased denitrification or fixed-nitrogen (N) loss; however, recent studies have suggested that not all N may be lost from these environments, with some N returning to the system via microbial dinitrogen (N(2)) fixation. We investigated denitrification and N(2) fixation in an intertidal lagoon (Catalina Harbor, CA), an environment characterized by bioturbation by thalassinidean shrimp (Neotrypaea californiensis). Field studies were combined with detailed measurements of denitrification and N(2) fixation surrounding a single ghost shrimp burrow system in a narrow aquarium (15 cm by 20 cm by 5 cm). Simultaneous measurements of both activities were performed on samples taken within a 1.5-cm grid for a two-dimensional illustration of their intensity and distribution. These findings were then compared with rate measurements performed on bulk environmental sediment samples collected from the lagoon. Results for the aquarium indicated that both denitrification and N(2) fixation have a patchy distribution surrounding the burrow, with no clear correlation to each other, sediment depth, or distance from the burrow. Field denitrification rates were, on average, lower in a bioturbated region than in a seemingly nonbioturbated region; however, replicates showed very high variability. A comparison of denitrification field results with previously reported N(2) fixation rates from the same lagoon showed that in the nonbioturbated region, depth-integrated (10 cm) denitrification rates were higher than integrated N(2) fixation rates (～9 to 50 times). In contrast, in the bioturbated sediments, depending on the year and bioturbation intensity, some (～6.2%) to all of the N lost via denitrification might be accounted for via N(2) fixation.     

Behavioural and physiological adaptations to a burrowing lifestyle in the snake blenny, Lumpenus lampretaeformis, and the red band-fish, Cepola rubescens

Observations have been made on the mode of burrow construction in the snake blenny, Lumpenus lampretaeformis , under laboratory conditions. It appears that head probing and lateral oscillations of the body are principally responsible for the excavation of the burrow which is completed within 24 h. The burrow structure has been analysed in detail, showing a mean depth of 7.2 cm with a maximum observed length of 73 cm, with most systems between 20 and 35 cm in length. Initially linear burrows with two openings are usually provided with a small side tunnel, giving the system a characteristic Y-shape.
Burrow irrigation was investigated for the first time in L. lampretaeformis. The mean duration of burrow irrigation, by flexions of the tail of the fish, was 21 s with over 13 min h⁻¹ spent in irrigating the burrow. The mean water displacement per irrigation period was 3.1 ml. The PO ₂ and PCO ₂ were measured in both surface water and within the burrow system of L. lampretaeformis. Surface water values for PO ₂ were high (> 150 Torr) and PCO ₂ low (<0.4 Torr). Hypoxic and hypercapnic conditions were measured in the burrow system itself, with PO ₂ values ranging between 57 and 129 Torr and PCO ₂ rising to > 1.3 Torr in some burrows.
A comparative study of Cepola rubescens burrows indicated similar surface water PO ₂ and PCO ₂ values as in L. lampretaeformis. Burrow water PO ₂ values ranged between 60 and 94 Torr, with PCO ₂ values as high as 1.5 Torr being recorded. These results are discussed in relation to the adaptation of both species to a burrowing lifestyle.     

The effects of temperature and salinity on ventilation behavior of two species of ghost shrimp (Thalassinidea) from the northern Gulf of Mexico: a laboratory study

Thalassinidean shrimp are among the most important bioturbators in coastal ecosystems. The species Lepidophthalmus louisianensis and Callichirus islagrande are found in dense aggregations (up to 400 burrows m⁻²) along sandy and muddy shores of the northern Gulf of Mexico. These shrimp actively ventilate their burrows to provide oxygen and eliminate wastes. In doing so, they expel nutrient-rich burrow water to the overlying water column, potentially altering nutrient cycling and benthic primary productivity. To develop a mechanistic understanding of the role of burrowing shrimp in nutrient processes, we must first examine how changes in environmental conditions alter the frequency, strength, and duration of ventilation. Field measurements of burrow temperature and salinity suggest that the burrow serves as a buffer from the highly variable conditions found in these estuarine, intertidal habitats. Temperatures at sediment depths >30 cm were generally warmer in winter and cooler in summer than at the sediment surface. Burrow salinities, measured at low tide, were consistently higher than adjacent open water. We used these measurements to parameterize laboratory studies of burrow ventilation in artificial burrows made of plastic tubing and in more natural sediment mesocosms, and studies of oxygen consumption in small glass containers. Rates of oxygen consumption and burrow ventilation by L. louisianensis were lower than those of C. islagrande, perhaps reflecting a lower overall activity rate in the former species which resides in less permeable sediments. Generally, increased temperature had a significant positive effect on oxygen consumption for both species. Salinity had no effect on oxygen consumption by L. louisianensis, reflecting the ability of this species to exist in a wide range of salinities. In contrast, oxygen consumption rates of C. islagrande, which is less tolerant of low salinity, were significantly higher at 35‰ than at 20‰. Ventilation rates were highly variable, and shrimp in artificial burrows tended to have consistently higher ventilation rates than those in sediment mesocosms. There is a trend toward more frequent ventilation at 30 °C for both species. Salinity had no effect on ventilation for either species. Our results suggest that thalassinideans exhibit highly variable and species-specific ventilation patterns that are more likely to be affected by temperature than salinity. Increased ventilation at higher temperatures seems to coincide with increased oxygen consumption at these temperatures, although a similar finding was not made for salinity treatments.     

Exchange of oxygen across the epicardial surface distorts estimates of myocardial oxygen consumption

The rate of oxygen consumption of isolated, Langendorff-circulated, saline-perfused hearts of guinea pigs, rats, and rabbits was measured using the classical Fick Principle method. The heart was suspended in a glass chamber the oxygen partial pressure, PO2, of which could be varied. The measured rate of oxygen consumption was found to vary inversely with the ambient (heart chamber) PO2. This result prevailed whether the chamber was filled with air, saline, or oil, and whether the pericardium was present or the heart was wrapped in Saran. The effect varied inversely with heart size both within and across species. It is concluded that the epicardial surface is permeable to oxygen which will diffuse either into or out of the heart as the PO2 gradient dictates. In either case the classically measured rate of oxygen consumption will be in error. The error can be large in studies of cardiac basal metabolism. A simple model is developed to describe the observed rate of oxygen consumption as classically measured. The measured rate is partitioned into two components: the true rate of oxygen consumption of the heart, and the rate of loss of oxygen by diffusive exchange across the epicardial surface. The latter component is proportional to the gradient of oxygen partial pressure from myocardium to environment and to the diffusive oxygen conductance of myocardial tissue. Application of the model allows the true rate of oxygen consumption of the heart to be recovered from measured values which may be considerably in error.     

The impact of polychaete (Nereis virens Sars) burrows on nitrification and nitrate reduction in estuarine sediments

The influence of Nereis virens Sars burrows on nitrification, denitrification and total nitrate reduction was assessed in poor (0.7% organic matter) and rich (2.0% organic matter) sediment from the estuary, Norsminde Fjord. The experiments were performed as assays of potential activity, since natural conditions proved impossible to simulate in the unpredictable burrow environment. The measurements were made in two microprofiles, extending 15 mm into the sediment from the surface and from the burrow wall lining. Both sediment types showed higher potential nitrification in the wall linings than in the surface sediment. This was positively correlated with the content of silt + clay particles and organic matter (i.e. the mucous lining of burrow walls). An elevated nitrate reduction activity was evident in the oxic layer of surface sediment. No such activity pattern was observed in the burrow walls. Denitrification accounted for 27–53 % of the total nitrate reduction. An empirical relationship between the ratio of predicted oxygen penetration into surface and wall sediment and the contribution of nereid burrows to bulk actual nitrification and nitrate reduction is presented. The burrow contribution to bulk nitrification was, in contrast to bulk nitrate reduction, very sensitive to variable oxygen penetrations. Thus, possible short-time changes in nitrate exchange across the wall lining will apparently be regulated by changes in nitrification activity rather than nitrate reduction activity.     

PCO(2) threshold for CNS oxygen toxicity in rats in the low range of hyperbaric PO(2).

Central nervous system (CNS) oxygen toxicity, as manifested by the first electrical discharge (FED) in the electroencephalogram, can occur as convulsions and loss of consciousness. CO(2) potentiates this risk by vasodilation and pH reduction. We suggest that CO(2) can produce CNS oxygen toxicity at a PO(2) that does not on its own ultimately cause FED. We searched for the CO(2) threshold that will result in the appearance of FED at a PO(2) between 507 and 253 kPa. Rats were exposed to a PO(2) and an inspired PCO(2) in 1-kPa steps to define the threshold for FED. The results confirmed our assumption that each rat has its own PCO(2) threshold, any PCO(2) above which will cause FED but below which no FED will occur. As PO(2) decreased from 507 to 456, 405, and 355 kPa, the percentage of rats that exhibited FED without the addition of CO(2) (F(0)) dropped from 91 to 62, to 8 and 0%, respectively. The percentage of rats (F) having FED as a function of PCO(2) was sigmoid in shape and displaced toward high PCO(2) with the reduction in PO(2). The following formula is suggested to express risk as a function of PCO(2) and PO(2) [abstract: see text] where P(50) is the PCO(2)for the half response and N is power. A small increase in PCO(2) at a PO(2) that does not cause CNS oxygen toxicity may shift an entire population into the risk zone. Closed-circuit divers who are CO(2)retainers or divers who have elevated inspired CO(2)are at increased risk of CNS oxygen toxicity.     

A new species of Mysidobdella (Hirudinida: Piscicolidae) from mysids along the California coast

Mysidobdella californiensis n. sp. is described from the mysid Holmesimysis sculpta from Bodega Bay on the central California coast and from Holmesimysis costata var. from San Pedro on the southern California coast. The internal anatomy of M. californiensis is similar to that of the only other species in the genus, Mysidobdella borealis from the north Atlantic Ocean, except that M. californiensis lacks the medial, unpaired seminal receptacle present in M. borealis. Externally, M. californiensis is slightly larger and more robust than M. borealis, with a much larger caudal sucker. The most striking difference between the species is the unusually large, trumpet-shaped, fluted oral sucker in M. californiensis. At Bodega Bay, the prevalence of M. californiensis on its host was 17% with an average intensity of 1.46 (range 1-3) leeches per host.     

Oxygen uptake,the circulatory system,and haemoglobin function in the intertidal polychaete Terebella haplochaeta (Ehlers)

The intertidal polychaete Terebella haplochaeta (Ehlers) shows a high degree of oxyregulation in declining pO₂ when confined to its burrow at low tide. This response is achieved by a number of adaptations to the respiratory system. The worm ventilates its burrow in a headward direction by rhythmical conractions of the body. The rate of these pulsations increases at low pO₂ and assists the circulation of the coelomic and vascular fluids. Haemoglobin in the vessels has a high affinity for oxygen and a sigmoidal equilibrium curve. Both the shape and position of the oxygen-binding curve are sensitive to changes in pH, pCO₂, and temperature in a way that suggests augmentation of oxygen delivery at low tide. The concentration of haemoglobin in the vessels is high and is further raised following warm acclimation, presumably to meet an increase in oxygen demand. The ultrastructure of the gills and blood vessels indicates a design for function at low oxygen tensions where diffusion distances must be short and surface areas large in order to enhance the rate of diffusion of oxygen from the near environment.     

Placental gas exchange in the guinea-pig: fetal blood gas tensions following the reduction of maternal oxygen capacity with carbon monoxide

The effect of CO hypoxia on the placental exchange of respiratory gases was studied in anaesthetized pregnant guinea-pigs near term. Fetal PO2 and PCO2 were measured by mass spectrometry from a blood gas catheter in the right atrium. Administration of 5 ml CO over 65 s reduced maternal oxygen capacity by 26%. There was a rapid fall in fetal arterial PO2 and a more gradual rise in fetal PCO2. It was shown in separate experiments that the carboxyhaemoglobin content of fetal blood did not alter greatly in the first few min. after CO administration, which is the interval within which fetal PO2 was seen to fall. The alteration in fetal gas tensions can therefore be ascribed to the increased oxygen affinity and reduced oxygen capacity occasioned by the presence of carboxyhaemoglobin in the maternal blood. The alteration in placental oxygen transfer was calculated from the experimental findings, using a mathematical model of placental gas exchange in the guinea-pig. The total reduction in the oxygen transfer was 32% of the initial value. It was calculated that the reduction in maternal oxygen capacity was responsible for about two-thirds of this decrease, the remainder being due to the increased oxygen affinity of maternal blood.     

The role of mounds in promoting water-exchange in the egg-tending burrows of monogamous goby, Valenciennea longipinnis (Lay et Bennett)

Valenciennea longipinnis spawns monogamously in a burrow. After spawning, the paired female constructs a conspicuous mound on the burrow by carrying and piling up substratum-derived materials while the male tends eggs in the burrow until hatching occurs. In this study, the mounds of V. longipinnis were tested in the field to confirm their function of promoting water-exchange in the burrow, and their ecological role was examined in relation to egg care by the male. The mound of V.longipinnis promoted water-exchange in the burrow, contributing to the provision of external oxygenated sea water into the burrow. Therefore, dissolved oxygen (DO) concentrations in the burrow with a mound were significantly higher than those without a mound. Although male egg-tending behaviour (e.g., fanning) may also promote water-exchange in the burrow, the water-exchange appeared to depend mainly on the hydrodynamic effect. Removals of the mound and paired female on the day of spawning led to high rates of egg-desertion by males. Since the frequency and time of fanning increase with a decrease of DO concentration in the burrow, the egg-desertion may result from an increased parental cost to males due to the decrease of water-exchange without a mound. This was supported by the fact that the DO concentrations on the day after mound removal were significantly lower in the egg-deserted burrows (measured before desertions) than in burrows not deserted by the male. Moreover, removals of paired females only also led to higher desertion rates. After removal of the female, the mound gradually collapsed by wave action and other factors, and the surface of the mound was covered with planktonic materials. Such a mound of poor quality may provide little water-exchange, which may lead to the egg-desertion by males. These results indicated that mound maintenance by females during the egg-tending period has an important role in the success of parental care by males.     

Cyclic gas exchange in the giant burrowing cockroach, Macropanesthia rhinoceros: effect of oxygen tension and temperature

The giant burrowing cockroach, Macropanesthia rhinoceros, is endemic to north-eastern Australia and excavates a permanent burrow up to 1m deep into soil. Using flow-through respirometry, we investigated gas exchange and water loss at three different oxygen tensions (21%, 10% and 2% at 20 degrees C) and temperatures (10, 20 and 30 degrees C at 21% oxygen). M. rhinoceros employ cyclic gas exchange (CGE) making the species by far the largest insect known to engage in discontinuous ventilation. CGE featured rhythmic bursts of CO(2) dispersed among inter-burst periods of reduced output. CGE was most commonly observed at 20 degrees C and degraded at <10% oxygen. Mild hypoxia (10% oxygen) resulted in a lengthening of the burst period by approximately two-fold; this result is complementary to oxygen consumption data that suggests that the burst period is important in oxygen uptake. When exposed to severe hypoxia (2% oxygen), CGE was degraded to a more erratic continuous pattern. Also, during severe hypoxia, total water loss increased significantly, although CO(2) release was maintained at the same level as in 21% oxygen. During CGE, an increase in temperature from 10 to 20 degrees C caused both water loss and CO(2) output to double; from 20 to 30 degrees C, CO(2) output again doubled but water loss increased by only 31%.     

Metabolic and ventilatory responses to hypoxia in two altitudinal populations of the toad, Bufo bankorensis

Effects of hypoxia on resting oxygen consumption (MO2), lung ventilation, and heart rate at different ambient PO2 were compared between lowland and high altitude populations of the toad, Bufo bankorensis. Resting MO2 decreased significantly in mild hypoxia (PO2 = 120 mm Hg) at 10 degrees C and in moderate hypoxia (PO2 = 80 mm Hg) at 25 degrees C in both altitudinal populations; however, resting MO2 did not differ significantly between the two populations. Numbers of lung ventilation periods (VP) and total inspired volume (VL) did not change with PO2 at 10 degrees C, but did increase at moderate and severe hypoxia (40 mm Hg), respectively, at 25 degrees C. Resting heart rates did not change during hypoxia and did not differ between altitude populations. The results suggest (1) the effect of PO2 change on MO2 should be considered in future studies involving transfer of anurans to a different altitude; and (2) the metabolic and ventilatory physiology in B. bankorensis does not compensate for the low temperature and PO2 at high altitude.     

Microcirculatory hematocrit and blood flow

Direct measurements from many laboratories indicate that the oxygen tension in skeletal muscle is significantly less than in the large veins draining these tissues. Harris (1986) has proposed that because of the parallel anatomic arrangement of large arterioles and venules in skeletal muscle, a counter-current exchange between these vessels can occur. He theorized that diffusion of O2 between arteriole and venule would lower the PO2 in the blood as it enters capillaries and result in a decreased tissue PO2 and an increase in large vein PO2. Calculations (Appendix) show that the amount of O2 transferred between arteriole and venule is inadequate to account for this difference in PO2 between tissue and veins due to the small surface area that is involved. It is well documented that the microcirculatory hematocrit ranges between 20 and 50% of that in the supply vessels. The reduced hematocrit lowers the oxygen content in these vessels and results in a low oxygen tension in the surrounding tissue. True arteriovenous shunts are not present in most skeletal muscles, but 15-20% of the microvessels represent thoroughfare or preferential flow channels. It is suggested that these vessels contain a greater than normal hematocrit to account for a conservation of red cell mass across the microcirculation. Furthermore, it is shown that the hematocrit in the preferential flow channels is an inverse function of the flow rate for any level of the microcirculatory hematocrit. The increased hematocrit raises the flow resistance in these vessels which reduces flow further and represents a positive feedback condition which may contribute to the intermittent and uneven flow patterns which are present within the microcirculation.(ABSTRACT TRUNCATED AT 250 WORDS)     

The function of hemocyanin in respiration of the blue crab Callinectes sapidus.

Blood PO2 in the blue crab Callinectes sapidus, a very active species of tropical origin, is lower at 22 degrees C than that of larger crabs in colder waters. These low oxygen levels permit its hemocyanin to be highly oxygenated at the gill, and to deliver almost half of its oxygen to the tissues in resting animals. Sustained muscular activity results in conspicuous decreases in blood PO2, pH and hemocyanin oxygenation. Although the venous reserve is fully utilized, hemocyanin oxygenation at the gill decreases so much that there is no change in its total quantitative function. The large Bohr shift becomes functional during activity, but its quantitative importance is not clear.     

Microscale oxygen distribution in various invertebrate burrow walls

Profiles of dissolved oxygen were measured in pore waters of unburrowed sediment and the burrow walls of seven invertebrate dwellings. Burrows studied include those of Corophium volutator, Heteromastus filiformis, Arenicola marina, Saccoglossus bromophenolosus, Clymenella sp., Hemigrapsus oregonensis and Cirriformia luxuriosa all from mudflats in Willapa Bay, Washington. These animals comprise a range of burrow architectures ranging from simple, unlined burrows to more complex, mucous lined burrows. Oxygen penetrated unburrowed sediment between depths of 0.4–2.6 mm, whereas oxygen penetrated the burrow walls from 0.3 mm to 2.3 mm. Three groups of burrows are recognized based on the oxygen diffusive properties relative to the unburrowed sediment including those that: (1) slightly impeded oxygen penetration, (2) clearly inhibited oxygen penetration, and (3) enhanced oxygen penetration. Differences in the diffusive properties of the burrow wall are related to the burrow microstructure and presumably the microbial communities living within the burrow microenvironment. The results of this study suggest that burrow shape and burrow‐wall architecture may play an important role in controlling the diffusion of oxygen, and possibly of other dissolved gases (i.e. CO₂, H₂S). The results further demonstrate that simplified assumptions (i.e. that bioturbation uniformly enhances oxygen diffusion into suboxic and anoxic sediments), while requisite for numerical modelling, are not necessarily representative of field data.     

Accurate quantification of the influence of benthic macro- and meio-fauna on the geometric properties of estuarine muds by micro computer tomography

This paper describes the novel application of high resolution micro computer tomography (microCT) to the quantification of the properties of marine biogenic structures. CT scanning has been used to examine sediments in the past but the resolution of most previous techniques has been dependent upon commercial medical CT scanners which only have a slice thickness of ≥ 0.625 mm. In addition adequate software has not previously been available to rapidly quantify all the properties of biogenic structures. The microCT technique developed here used a standard core sample of estuarine sediment and new software was developed to calculate the axial variation of the following burrow parameters: number, diameter, volume, surface area and density. The increased resolution has resulted in the first quantification of meiofaunal burrow structures.A test core has shown, as an example, that the total volume of burrows created by macrofaunal organisms decreased from 827 mm³, within the top 15 mm of the core, to 204.2 mm³ at a depth 60 -75 mm within the core. Total burrow surface area decreased from 1883 mm² to 512 mm², for these depth ranges, respectively and burrow diameter ranged from 2.37-2.58 mm, remaining fairly constant between depths. Meiofaunal burrow structures decreased from 1.3-0.1 mm³ within the top 6 mm of the core with burrow surface area decreasing from 33.52-3.4 mm². Again, burrow diameter remained relatively constant, ranging from 0.23-0.25 mm.Quantification to this resolution is required to identify the impact of infaunal organisms on factors such as oxygen penetration, vertical and horizontal (across burrow walls) gradients in redox conditions and chemical/nutrient speciation and flux. The quantification of these burrow properties will improve the ability to examine the interrelationships between chemical, physical and biological processes and their role in ecological functioning. The present study indicates that there is potential for further development of this software to allow more detailed analysis of burrow structures and surface features including parameters such as burrow length, shape and sediment surface roughness.